测定某水样的生化需氧量时，培养液300mL，其中原水100mL。水样培养前、后的溶解
题型：单项选择题
问题：
测定某水样的生化需氧量时，培养液300mL，其中原水100mL。水样培养前、后的溶解氧含量分别为8.39mg/L和1.41mg/L。稀释水培养前、后的溶解氧含量分别为8.87mg/L和8.79mg/L。该水样的BOD5值是（）。
A．10.4mg/L
B．20.8mg/L
C．15.4mg/L
D．18.6mg/L
题型：单项选择题
根据短文内容，从下面的A-F选项中选出能概括每一段主题的最佳选项，并在答题卡上将该选项涂黑。选项中有一项为多余项。
How to Become a Healthy Person?
小题1:
The following are some healthy lifestyle tips that will help you on how to be a healthy person. We all know that our minds control our actions, and so does our thoughts, and this is why the happy and optimistic people live longer and healthier! In this modern world, we often pay more attention to the negative（负面的，消极的） than the positive! Believe it or not,the more negative thoughts you have in your mind,the more outcomes of you efforts will be.No matter what the situation is, you need to change your thoughts and practice to pay attention to the positive.
小题2:
You need to give enough rest to your body and mind which will only come from a good sound eight hours sleep. This will not only make your body and mind fresh,but also make you more active and relaxed. Some tips for better sleep would be to stay away from such things as so-called “energy drinks”. If you want real health, sleep is all you need to have.
小题3:
Have you seen the group of old people in the park who form a round circle and start laughing as if they would win a million dollars for it ? No matter how funny it looks, the benefits of laughter are a way beyond our imagination. If you feel like smiling, just smile! No matter what, wear that beautiful smile on your lips and make sure it is always there.
小题4:
Eating healthy foods and balancing it with the right amount of exercise is extremely important. Try to eat as much fruit and vegetables as possible. Such food makes you feel light and active! Wake up early in the morning and start with proper exercise.A 30-minute walk or run will not only make you physically healthy and active, but also make you more flexible and your mind smart.
小题5:
The way you look upon yourself is the way you look upon your life. It is very important for a person to have self-esteem(自尊)， for it is your attitude that decides your life. No matter what you have done so far, it’s the way you look upon yourself that really matters. Think what person you want to be and keep to it. Work hard towards becoming the person you want to be.